1. Field of the Invention
This invention relates to the field of anesthesiology simulation to provide a mannequin for use in training anesthesiologists, and in particular, to a simulated human lung that can be utilized in the mannequin for the training of anesthesiologists.
2. Description of the Prior Art
The human lung is an organ that is activated by contractions of the diaphragm muscle to provide an intake of oxygen O.sub.2 from the atmosphere for transfer to the person's blood and to expel CO.sub.2 which is received from the blood for exhalation back into the atmosphere. When a patient is anesthetized for medical treatment, such as surgery, a muscle relaxant drug is administered by a qualified anesthesiologist to prevent all body muscular contraction to inhibit patient movement during the medical treatment. The muscle relaxing drug affects all the muscles in the body, including the diaphragm, requiring that the patient be artificially ventilated while anesthetized to provide proper oxygen O.sub.2 intake and CO.sub.2 output. Since the patient cannot breathe normally or voluntarily while under a muscle relaxant drug, the patient's entire breathing is completely dependent on the ventilating equipment. Thus, one of the most important functions that an anesthesiologist must perform is the proper ventilation of a patient while anesthetized. The insertion and proper placement of respiratory tubes in the trachea requires the skilled anesthesiologist. Misalignment or misplacement of the O.sub.2 intake tube can divert O.sub.2 into the stomach instead of the lungs, resulting in severe patient injury or death. Equipment failure of the ventilating equipment can also result in patient injury and is something that must be constantly monitored by the anesthesiologist during the ventilation process. Failure of the proper amount of O.sub.2 to flow can also result in an injury or death to the patient.
Heretofore, almost all training of anesthesiologists has been by having the student doctor observe numerous actual patients being anesthetized by one or more skilled anesthesiologists. The anesthesiologist must remain present during the patient treatment or operation for the entire period that the patient is being ventilated. Thus, in the training cycle, typically, the students will also be required to spend several hours as an observer. Such a training procedure is extremely costly and provides little guarantee that the student will be able to observe all possible emergency problems that can arise during the time period that the patient is anesthetized. Obviously, during an actual patient operation, there is no opportunity to practice typical or even unexpected emergencies that could happen during the actual process.
The present invention is utilized within an anesthesiology simulator and is one of the very critical elements with regard to the anesthesiology process with respect to ventilation to provide effective simulation of a patient being anesthetized, especially with respect to the patient respiratory system. The present invention provides for a simulated human lung that can simulate spontaneous breathing of the human lungs and can simulate the ventilated breathing of a human lung with the entire system fitting comfortably within a mannequin that is used as part of the overall simulation. Further, the present invention can provide extreme accuracy in simulating dynamic lung compliance and resistance variations, oxygen content sensing of the inspired air, and injection of carbon dioxide into the lungs to simulate the human body's physiological production of carbon dioxide.
The use of simulation for anesthesiology has been done at some universities in the United States, such as the University of Florida at Gainesville, Fla., and at Stanford University in Palo Alto, Calif. The University of Florida at Gainesville has employed a mechanical lung as part of their anesthesiology simulator. Although the system works well, it is large and is not maintained within the mannequin chest cavity. Dynamic lung compliance and resistance changes are done mechanically and often, the simulation exercise is stopped in order to change parameters.
U.S. Pat. No. 3,520,071, issued to S. Abrahamson et al. Jul. 14, 1970, shows an anesthesiological training simulator. Although the device shown in this patent includes chest movement, complex lung simulation is not achieved. U.S. Pat. No. 4,917,080, issued to Bayerlen Apr. 17, 1990, describes a method for controlling a ventilating apparatus using a simulator arrangement. This method uses an adjustment selected according to patient data which is changed for optimization after a workin time period. U.S. Pat. No. 4,797,104, issued to Laerdal et al. Jan. 10, 1989, describes a system for testing performance of cardio-pulmonary resuscitation, which includes the use of a mannequin. U.S. Pat. No. 4,878,388, issued to Loughlin et al. Nov. 7, 1989, describes a method for simulating gas exchange during ventilation that permits simulation of physiological functions occurring during anesthesia, such as the uptake and release of anesthetic agents.